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1st September 2019, 15:17 #1
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How to realize inductor from transmission line (microstrip and CPW lines)
Hi, I am reading the paper "Broadband Impedance Matching Network for RF Power Amplifiers" and came across idea of realizing Inductor using microstrio line.
(1)As per the above formula, I can find what is the required length of the line for that particular inductor value. Anyone knows the same kind of formula for CPW line? And how do I know what should be the charateristic impedanced of the line, are there any conditions or procedures to choose it?.
(2)But as per below formulas also we can get inductance.
I know that (2) can be used while doing stub matching but we can also use (1) for matching, however it is just the substitutuon of inductor. I want to know which one to use when and any more insight on this. Thanks.Last edited by circuitking; 1st September 2019 at 15:28.

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1st September 2019, 16:15 #2
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Re: How to realize inductor from transmission line (microstrip and CPW lines)
It is same.
Use transimission line calculator which supports CPW.
They are all same.
Learn and understand very basic things surely.
Consider how to realize short.
Simply if it is difficult to realize short, short stub is not chosen.
If you use laser trimming, you have no option except for open stub.
Learn actual measurement not EDA Tool Play.Last edited by pancho_hideboo; 1st September 2019 at 16:22.

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1st September 2019, 17:27 #3
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Re: How to realize inductor from transmission line (microstrip and CPW lines)
CPW cannot be used for Inductor Realizations.Especially if the frequency is not sufficiently high, making an inductor by using Transmission Lines is not practical at all..

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1st September 2019, 17:46 #4

3rd September 2019, 08:11 #5
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Re: How to realize inductor from transmission line (microstrip and CPW lines)
The simplest microstrip inductor would be from a microstrip line without ground (the ground decrease somehow its inductance).
The inductance of an isolated (no groundplane), high impedance microstrip line (W << W(Zo)) is given approximately by:
L(nH/mm) = 0.2*{ln[l/(W+t)]+1.193+0.2235(W+t)/l}
where W is the width of the strip line, t is the metal thickness, and l is length.

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3rd September 2019, 14:18 #6
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Re: How to realize inductor from transmission line (microstrip and CPW lines)
CPW stands for coplanar waveguides. Transmission lines can be realized onchip using coplanar metals as GroundSignalGround configuration. It can also be realized by routing the signal trace on a different metal layer and ground on a different metal layer. Then its no longer CPW.
How to choose Z0?
Increasing Zo will mean that you get the same inductance for a shorter length of line > lesser losses. Also, the bandwidth of matching using transmission lines increases when the impedance to be matched and the characteristic impedance are close to each other. Its an iterative process to get it right.
I also hope you realize that the first expression comes directly from the algebraic manipulation of a shorted stub.
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